(1) A procedure for the preparation of serum macrophage stimulating factor by Sephadex gel electrofocusing was developed. (2) The nature of the heterogeneity of immunoglobulins in electrofocusing (EF) was elucidated. This provides the basis for an improved clinical analysis for oligoclonal antibodies by gel electrophoretic methods. (3) hCG of high specific activity was isolated from commercial material in a single-step procedure, using re-stacking.